The Base of Nutritional Support for the Gray Snapper (Lutjanus Griseus): An Evaluation Based on a Combined Stomach Content and Stable Isotope Analysis
Abstract:A combined stomach content and stable isotope analysis was used to determine if seagrass provides a base of nutritional support to the gray snapper, Lutjanus griseus. The results provided a quantitative evaluation of the relative contribution of carbon and nitrogen from various primary organic sources to gray snapper taken from each a mangrove and a seagrass dominated location in south Florida. Stomach content analysis revealed that gray snapper from the two areas had similar diets which were primarily composed of penaeid shrimp (>60%). Isotopic results provided a distinction between food webs on the basis of carbon values. The δ13C of components from the seagrass location were greater than –17‰ in contrast to values of less than –19‰ for those from the mangrove area. Quantitative estimates indicated that gray snapper from the seagrass area derived more than 90% of their carbon and nitrogen from sediment or water column particulate organic matter. Gray snapper from the mangrove area were supplied by carbon and nitrogen from these sources in addition to detritus. The main contributors appeared to be particulate organic matter from the water column and the brackish water grass, Ruppia maritima. Together, these sources accounted for 35 to 100% of the ultimate source of prey item dietary carbon and nitrogen. These results suggest that within both food webs carbon and nitrogen are transferred from a detrital base by similar mechanisms and emphasize the use of multiple isotopes as a tool for quantitatively evaluating food webs.
Document Type: Research Article
Publication date: January 1, 1989
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